Abstract
Candida albicans is a human opportunistic pathogen that causes superficial and life-threatening infections. An important reason for the failure of current antifungal drugs is related to biofilm formation, mostly associated with implanted medical devices. The present study investigated the synergistic antifungal efficacy of low-frequency and low-intensity ultrasound combined with amphotericin B (AmB)-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (AmB-NPs) against C. albicans biofilms. AmB-NPs were prepared by a double-emulsion method and demonstrated lower toxicity than free AmB. We then established biofilms and treated them with ultrasound and AmB-NPs separately or jointly in vitro and in vivo The results demonstrated that the activity, biomass, and proteinase and phospholipase activities of biofilms were decreased significantly after the combination treatment of AmB-NPs with 42 kHz of ultrasound irradiation at an intensity of 0.30 W/cm(2) for 15 min compared with the controls, with AmB alone, or with ultrasound treatment alone (P < 0.01). The morphology of the biofilms was altered remarkably after joint treatment based on confocal laser scanning microscopy (CLSM), especially in regard to reduced thickness and loosened structure. Furthermore, the same synergistic effects were found in a subcutaneous catheter biofilm rat model. The number of CFU from the catheter exhibited a significant reduction after joint treatment with AmB-NP and ultrasound for seven continuous days, and CLSM and scanning electron microscopy (SEM) images revealed that the biofilm on the catheter surface was substantially eliminated. This method may provide a new noninvasive, safe, and effective therapy for C. albicans biofilm infection.